Excited frame vibratory conveying devices are well known in the art. For example, U.S. Pat. No. 4,313,535, shows a typical excited frame conveying apparatus. The teaching of this patent is incorporated by reference herein. Apparatuses of this type include a vibratory drive which is mounted on an elongated frame, and which rests on a factory floor or other supporting structure. Extending upwardly from the frame, and inclined in the direction of the intake or in-feed of the conveyor are a multiplicity of planar shaped, or leaf springs. An elongated conveyor or product transporting bed is mounted on the distal ends of each of these leaf springs and is supported by them in a generally parallel relationship relative to the frame, and in a substantially horizontal orientation. Due to the resiliency of the respective leaf springs, the product conveying bed is capable of moving relative to the underlying supporting frame in response to a force supplied to the bed by the vibratory drive. During the operation of the apparatus, the aforementioned vibratory drive produces an oscillating vibratory force which is typically generated by counter-rotating eccentric weights which are subcomponents of the vibratory drive. Because the vibratory drive is mounted on the frame, it imparts a vibratory motion to the frame, which is then transferred through the attached leaf springs to the conveyor bed. As a result, the product transporting bed vibrates at substantially the same frequency as the vibratory drive and frame. In operation, if the conveyor bed is displaced from its at-rest position, and then allowed to oscillate freely, it will oscillate at substantially its natural, or harmonic frequency. This natural frequency of the bed is dependent, at least in part, upon the combined spring constant, the number of springs supporting the bed, and the mass of the conveyor bed.
As compared with other designs of vibratory conveyors, excited frame conveyors, as a general matter, impart less vibrational and other forces to the underlying floor or other supporting structure because of its relatively light weight, and small vibrational amplitude of the frame as compared to the vibrational amplitude of the product conveying bed. The low level of vibrational force transferred to the surrounding supporting structure is a major advantage of the excited frame vibratory conveyor designs employed in the past.
Heretofore, these aforementioned leaf or planar springs, or so-called “vibratory conveyor arms” have been fabricated using what has been termed as “uni-directional” construction. In particular, filaments of fiberglass, all of which are oriented in spaced, substantially parallel relation, are bonded into a narrowly rectangular cross-sectional shape by the use of resins and epoxies of various types. For example, the product, Scotchply™ which is manufactured by the 3M Company has been utilized, heretofore in the fabrication of these vibratory conveyor arms. Vibratory conveyors utilizing this uni-directional construction are most easily understood by a review of U.S. Pat. No. 6,460,680. In this U.S. patent, the conveyed product travels in a substantially linear direction down the length of the vibratory conveyor bed. The conveyor bed stroke, that is, the resilient oscillating movement of the springs of the bed, is typically about three-eights of an inch in vibratory conveyors of this design. The frame employed with same is typically motionless during operation. It should be understood that the uni-directional construction of the vibratory conveyor arms works well with conveyors of this design for most product conveying applications. The bed and frame mounting brackets (and which are often referred to as arm clips), are mounted respectively on the conveyor frame, and the moveable bed. They are aligned during the fabrication of the conveyor. Misalignment of the two arm clips that couple the vibratory leaf spring to the underlying frame, and overhead conveyor bed will typically result in a premature spring failure. When this occurs, the fiberglass filaments encased within the vibratory conveyor arms will typically break, resulting in a significant reduction in the spring constant associated with the respective vibratory conveyor arms. It should be understood that the spring constant associated with the respective vibratory conveyor arms is the ability of the leaf spring to resist, and then return energy back into the vibrating conveyor system. When the filaments in the individual leaf springs begin to break, a catastrophic failure begins in the overall conveying system. In this regard, the conveyor system load that was being carried by the springs which are now compromised will then be transferred to other conveyor arms. Since the total spring constant has now been compromised with the loss of one vibratory conveyor arm, the bed stroke will usually increase. As the bed stroke increases, stress will increase on the remaining vibratory conveyor arms, and the result will be that more of these structures will begin to break or fail.
As noted, above, the uni-directional type construction of the leaf springs used in a vibratory conveyors such as shown in U.S. Pat. No. 6,460,680 works with a great deal of success. However, the industry has long perceived a need to provide vibratory conveyors of the type described in the aforementioned patent, but which are further operable to move a given product along a non-linear or semi-circular paths of travel. An example of such a construction is shown in U.S. Publication No. 2011/0005896, which identifies a number of inventors including the present inventor, David Hufford. The conveying device as seen in U.S. Publication No. 2011/005896, has a construction which provides or causes semicircular or circular movement of a given conveyed product. The arrangement, as shown in this publication, provides for vibrating circular motion, and the leaf springs employed with same experience to some degree, misalignment and twisting as a function of the normal operations of the described machine. The uni-directional leaf springs as described above have shown that they cannot tolerate a high degree of this motion, and consequently, failures of the leaf springs have been experienced heretofore in this machine design.
Therefore, a perceived need exists for the development of a new leaf spring which may be used on a vibratory conveyor, and which avoids the detriments associated with the use of previous spring constructions employed with the vibratory conveyors shown in the prior art.